Wednesday, 14 September 2016

"Glioblastomas are one of the most malignant forms of brain tumour and
are difficult to surgically remove because the tumour cells invade the
surrounding healthy brain tissue. Glioblastomas also affect the
microglia -- immune cells of the brain -- in such a way that they
stimulate the tumour cells instead of attacking them.
The multi-national research group has previously shown that
pro-inflammatory activation of microglia is controlled by a group of
enzymes called caspases. In the present study, they sought to examine if
the way the cancer cells affect microglia also includes similar
mechanism. By cultivating microglia and glioblastoma cells together, the
researchers were able to show that the cancer cells inhibit caspase-3
activity in the microglia.
"We show that it's the same inhibition of caspase-3 that causes the
microglia to stimulate the tumour cells instead of attacking them," says
Bertrand Joseph, Principal Investigator at Karolinska Institutet's
Department of Oncology-Pathology. "When we removed caspase-3 from the
microglia in a glioblastoma mouse model, the tumours grew more quickly."
According to the study authors, their results demonstrate that the
glioma cells use a nitric oxide-dependent mechanism to force microglia
to modify caspase-3 to form a tumour-stimulating form of these cells.
"Two things surprised us," says Bertrand Joseph. "First and foremost,
that affecting the signalling mechanism between glioblastoma cells and
microglia that we discovered has such a major effect on tumour growth.
Secondly, that basal caspase-3 activity, which is often considered to be
an absence of activity, fulfills essential function in regulating
microglia cell behavior."